Antenna apparatus and in-line calibration system for same

Abstract

A calibration system includes a beamformer lattice including at least a first beamformer, the first beamformer corresponding to a first subset of antenna cells of a plurality of antenna cells including a plurality of feed lines extending between the first beamformer and each of the first subset of antenna cells, and the first beamformer including a first calibration section for comparing a reference signal to a non-reference signal; and a first calibration line corresponding with the first beamformer, wherein the first calibration line is configured to deliver a first reference signal (mTx) from the first beamformer to be received by a first antenna feed line for comparison with a first non-reference signal (Rx) in the first beamformer, and/or wherein the first calibration line is configured to deliver a second non-reference signal (Tx) from a second antenna feed line for comparison with a second reference signal (mRx) in the first beamformer.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
       1. An antenna calibration system for a phased array antenna, the antenna calibration system comprising:
 a beamformer lattice including at least a first beamformer, wherein the first beamformer corresponds to a first subset of antenna cells of a plurality of antenna cells including a plurality of feed lines extending between the first beamformer and each of the first subset of antenna cells, wherein the feed lines are on a first layer, and wherein the first beamformer includes a first calibration section for comparing a reference signal to a non-reference signal; and 
 a first calibration line corresponding with the first beamformer, wherein the first calibration line is on a second layer, the first and second layers being separated by a ground laver, wherein the first calibration line is configured to deliver a first reference signal (mTx) from the first beamformer to be received by a first antenna feed line for comparison with a first non-reference signal (Rx) in the first beamformer, and/or wherein the first calibration line is configured to deliver a second non-reference signal (Tx) from a second antenna feed line for comparison with a second reference signal (mRx) in the first beamformer. 
 
     
     
       2. The system of  claim 1 , wherein the first calibration line is electrically coupled to at least a first portion of the plurality of antenna feed lines. 
     
     
       3. The system of  claim 1 , wherein the ground layer includes a cutout portion for allowing electrical coupling between the antenna feed lines and the first calibration line. 
     
     
       4. The system of  claim 2 , wherein the calibration line coupling is directional. 
     
     
       5. The system of  claim 2 , wherein the calibration line coupling is a weak coupler having a coupling level in the range of −20 dB to −41 dB. 
     
     
       6. The system of  claim 1 , further comprising a second calibration line corresponding with the first beamformer, wherein the second calibration line is configured to deliver the first reference signal (mTx) from the first beamformer to be received by a third antenna feed line for comparison with a third non-reference signal (Rx) in the first beamformer, and/or wherein the second calibration line is configured to deliver a fourth non-reference signal (Tx) from a fourth antenna feed line for comparison with the second reference signal (mRx) in the first beamformer. 
     
     
       7. The system of  claim 6 , wherein the second calibration line is electrically coupled to at least a second portion of the plurality of antenna feed lines. 
     
     
       8. The system of  claim 6 , wherein the first and second calibration lines include a combiner/divider for splitting a signal path for the first reference signal (mTx) from the first beamformer onto the first and second calibration lines and for combining a signal path for the second reference signal (mRx) from the first and second calibration lines to the first beamformer. 
     
     
       9. The system of  claim 1 , wherein the beamformer lattice includes at least a second beamformer, wherein the second beamformer corresponds to a second subset of antenna cells of the plurality of antenna cells, and wherein the second beamformer includes a second calibration section for comparing the reference signal to an additional non-reference signal, and wherein the first calibration line corresponding with the first beamformer communicates with the first and second beamformers. 
     
     
       10. The system of  claim 9 , further comprising an additional calibration line corresponding with the second beamformer, wherein the additional calibration line is configured to deliver a first additional reference signal (mTx) from the second beamformer to be received by a first additional antenna feed line for comparison with a first additional non-reference signal (Rx) in the second beamformer, and/or wherein the additional calibration line is configured to deliver a second additional non-reference signal (Tx) from a second additional antenna feed line for comparison with a second additional reference signal (mRx) in the second beamformer. 
     
     
       11. The system of  claim 10 , wherein the first calibration line corresponding with the first beamformer is coupled with the additional calibration line corresponding with the second beamformer, such coupling configured for communicating calibration information from either of the first and second beamformers to the other of the first and second beamformers, or both from the first beamformer to the second beamformer and from the second beamformer to the first beamformer. 
     
     
       12. The system of  claim 11 , wherein the first calibration line corresponding with the first beamformer is coupled with at least three other calibration lines corresponding with at least three other beamformers. 
     
     
       13. The system of  claim 1 , further comprising a stack patch antenna assembly defining the plurality of antenna cells. 
     
     
       14. The system of  claim 13 , further comprising a PCB assembly coupled to the stack patch antenna assembly and the beamformer lattice, the PCB assembly made up from a plurality of layers, wherein a first layer is an antenna ground layer having a slot feed to electrically couple each of the plurality of antenna cells of the stack patch antenna assembly to a beamformer in the beamformer lattice, wherein the first layer is spaced from a backing ground layer defining a plurality of cavities between the first layer and the backing ground layer, each cavity associated with one of the plurality of antenna cells, the PCB assembly further including an intermediate layer between the first layer and the backing layer, wherein the intermediate layer includes cavity portions and non-cavity portions, wherein the non-cavity portions are configured to support electrical features disposed outside the cavities. 
     
     
       15. The system of  claim 14 , wherein the PCB assembly includes a plurality of ground vias between the first layer and the backing ground layer defining the cavities. 
     
     
       16. The system of  claim 14 , wherein the slot feed is dual circularly polarized with separate receiving and transmitting ports. 
     
     
       17. The system of  claim 14 , wherein a second layer of the PCB assembly includes a 90-degree hybrid coupler. 
     
     
       18. A method for antenna calibration, comprising:
 obtaining a beamformer lattice including at least a first beamformer, wherein the first beamformer corresponds to a first subset of antenna cells of a plurality of antenna cells including a plurality of feed lines extending between the first beamformer and each of the first subset of antenna cells, wherein the feed lines are on a first layer, and wherein the first beamformer includes a first calibration section for comparing a reference signal to a non-reference signal; and 
 calibrating the beamformer lattice using a first calibration line corresponding with the first beamformer, wherein the first calibration line is on a second layer, the first and second layers being separated by a ground layer, wherein the first calibration line is configured to deliver a first reference signal (mTx) from the first beamformer to be received by a first antenna feed line for comparison with a first non-reference signal (Rx) in the first beamformer, and/or wherein the first calibration line is configured to deliver a second non-reference signal (Tx) from a second antenna feed line for comparison with a second reference signal (mRx) in the first beamformer.